intel/blorp: Add indirect clear color support to mcs_partial_resolve

intel/blorp: Add indirect clear color support to mcs_partial_resolve

This is a bit complicated because we have to get the indirect clear
color in there somehow.  In order to not do any more work in the shader
than needed, we set it up as it's own vertex binding which points
directly at the clear color address specified by the client.

Acked-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>